ca95f,
You said you had updated the firmware. Please clarify exactly how you did this and what version of OS you actually have on your N800 at the moment. You're not still running OS 2007 perchance are you?

I'm running OS 2008, upgraded it immediately I bought my device - and I got mine brand new. It was practically the first thing I did.

You might want to read up the FAQs and see if you followed the right procedure for an OS 2008 and beyond upgrade.

Perhaps you have indeed done everything right, but I can't tell, so, my best advice is to double check everything over again.

If it reads some cards and not the others, then it is possible that the OS might be an older version (can't remember if OS 2007 will read SDs beyond 2GB, thought it would though). Then again, it is possible that the other cards have been somehow corrupted (modified?) in some unexplainable way by the cameras they've been in.

As a general rule, I do not mix SDs between Digital Camera's and Hand held PCs. I recall formatting problems once in the distant past too - with an Ipaq 5545 or something.

Check all of the above points meticulously and you might be able to fix the N800 by simply re-installing the OS from scratch. I've had several Windows Mobile Smartphone devices suddenly go berserk on me and the only cure was to re-install the Windows OS (or better still, upgrade it to the next version up for better stability) from scratch, wiping ALL previous data. Always worked.

A similar approach to the N800 will probably fix it good.
However, you must proceed with caution, double check yourself every inch of the way, and avoid haste when doing the OS upgrade.

Hope you succeed in getting it working properly again.
The N800 in my opinion is a rare well put together device (despite any perceived short comings), which already has a cult following. This was one of Nokia's finest hours in innovation.

I still look at mine in awe, 11 months after I got it.
It's my SAT NAV, MP3 player, FM Radio, Digital Picture Display, for receiving High Res pics from my phone via bluetooth, Weather Station, Portable Web browser, a nice "Toy" (with the Star Trek LCARS theme running on it, it helps me fulfill my fantasy of holding a true Star Trek PADD device in my hands - hence, a "Toy" albeit fully functional!). And every so often, I get to watch NASA TV on it, streamed via the internet. Nothing beats watching the Astronauts working on the ISS or a Space Shuttle in orbit. It has so many free programs, I can't use them all, yet I'm absolutely satisfied with it.

Sorry, got carried away.
Hope my advice helps you further ca95f.
My apologies if you've done it all already - g'night from London


Thunderstorm.

ca95f, I have no idea. Mine, and seemingly everyone else's, works with almost all cards.

Yep, check the software version. The latest OS2007 release as well as the OS2008 releases should work. The early OS2007 release didn't.

You are using a Sandisk adapter with your SDHC card? If so, forget about it. You need a Mini SD adapter (a cheap one from eBay), and your card should work with no problems. I thought that the branded one would work (A Sandisk Mini sd reader), but I was told that it wouldn't.